The present invention relates to an improved lock and block system for holding in a preselected position the compression ram (blocking ram) on which is mounted the movable platen of a hydraulic injection molding machine. One aspect of the invention relates to improvements in the lock and block system wherein the compression ram supports a plurality of longitudinally movable spacer rings and defines a lock recess by spacing apart at least one of said rings from an opposite side of said lock recess.
Heretofore, hydraulic injection molding machine for exerting large clamping forces (e.g. 1000 tons clamping force and larger) have commonly used a lock-and-block system to hold the moving platen into position during the injection part of a molding process. Typically, this involves locking the ram on which is mounted the moving platen in position once it has been fully advanced to a position where the mold is closed and ready to receive plastic or other material under pressure. Also, typically, the locking means comprises a key or lock member which moves laterally out of the machine to engage a lock recess fashioned on the distal portion of the ram. In turn, the ram is a member which is moved longitudinally of the machine to assist in positioning the moving platen. The engagement of the lock or key with the lock recess is typically called a lock-and-block system.
The prior art also typically provides the lock recess by providing on the ram distal end a series of spaced apart flanges. The space between each two flanges comprises the lock recess into which the aforesaid lock can be moved. A plurality of such recesses are provided to permit the molding machine to be set up or to be adjusted for a number of different mold heights. This construction has ordinarily resulted in the mold clamping force being applied to one of the flanges in such manner as to flex the flange. Repeated force application on these flanges has on occasion led to fatigue failure with disastrous results to the machine structure.
The present invention is directed to an improved lock-and-block construction which greatly reduces and, indeed, may even eliminate fatigue failure, provides a more economical and reliable construction, and employs materials that are easier to handle and easier to fabricate. For example, the prior art flanges had the load or force applied close to their periphery and were often made of carefully machined bearing steel, whereas the present invention employs a ductile cast iron ring that is loaded in compression.
The present invention provides an improved blocking ram construction in a lock-and-block clamping force applying means which holds in a fully advanced position the movable platen of a hydraulic injection molding machine by engaging with a laterally moving key a lock recess provided in the tail section of the blocking ram which ram moves longitudinally through the stroke of the machine and holds the platen in such a manner that the key or lock fits the lock recess to block the ram and platen from any substantial movement away from the fully advanced position. The improved construction comprises: the tail section having a rear segment; a plurality of spacer rings mounted on the rear segment; a front section of said ram having a preselected diameter and which is secured to the moving platen and extends longitudinally a portion of the distance to the ram tail section; the rear segement has a cylindrical sleeve portion of a diameter less than said ram front section diameter; each ring of said plurality of annular spacer rings has an outer diameter substantially that of said ram front section, a predetermined longitudinal length, front and rear faces that are substantially parallel and an inner diameter approximately but slightly larger than that of said sleeve portion, at least one of said rings being movable longitudinally on said cylindrical sleeve portion, the longitudinal dimensions of the respective rings providing means for mold height adjustment; and the lock recess is provided by the longitudinal dimension between the opposing faces on any two selected rings and longitudinally of a size to receive the key. Thus, the machine can be adjusted so its blocking ram moves to a preselected one of a number of predetermined advanced positions which is coincident with the location of said recess whence the platen can be moved to the fully advanced position and, if molds be present, to hold the same closed while the lock-and-block construction resists opening of the mold during a molding procedure.